ALBANY — This doesn’t bode well for New York’s congressional Democrats: Freshman Rep. Scott Murphy’s once-comfortable lead over upstart Republican Chris Gibson has suddenly become a 9-point deficit.

The latest Siena poll yesterday shows Gibson — a retired Army colonel with a Ph.D. in government — leading Murphy 51 to 37 percent in the sprawling Albany-area congressional district. Just last month, he trailed Murphy 37 to 54.

The territory had long been in GOP hands until Democrat Kirsten Gillibrand upset incumbent Republican John Sweeney in 2006.

The survey found Gibson made huge gains among independents, turning a 28-point deficit into a 7-point lead, but he also shored up his base in the heavily Republican district.

Last month he led 59-32 among Republicans. Now he’s leading, 76-18.

“Republican voters have come home to Gibson,” said Siena pollster Steve Greenberg.

Republicans outnumber Democrats 187,000 to 125,000 in the district, which stretches from the northern outskirts of Poughkeepsie to the Adirondacks.